Circular RNAs (circRNAs) are a novel type of noncoding RNAs that modulate the pathogenesis of multiple diseases. Nevertheless, the role of circRNAs in diabetic nephropathy (DN) pathogenesis is still ambiguous. In the current study, our team aims to investigate the expression profiles of circRNAs in DN and identify the function of circRNA on mesangial cells. CircRNAs microarray analysis revealed dysregulated circRNA in db/db DN mice, and circRNA_15698 was validated to be upregulated in both db/db mice and mouse mesangial cells (SV40-MES13) that were exposed to high glucose (25 mM) using real-time polymerase chain reaction. Loss-of-functional experiments showed that circRNA_15698 knockdown significantly inhibited the expression levels of collagen type I (Col. I), collagen type IV (Col. IV), and fibronectin. Moreover, the cellular localization of circRNA_15698 was mainly in the cytoplasm. Bioinformatics tools and luciferase reporter assay confirmed that circRNA_15698 acted as a 'sponge' of miR-185, and then positively regulated the transforming growth factor-beta 1 (TGF-beta 1) protein expression, suggesting a circRNA_15698/miR-185/TGF-beta 1 pathway. Further validation experiments validated that circRNA_15698/miR-185/TGF-beta 1 promoted extracellular matrix (ECM)-related protein synthesis. In summary, our study preliminarily investigates the role of circRNAs in mesangial cells and ECM accumulation, providing a novel insight for DN pathogenesis.